From patchwork Tue Feb 13 02:05:10 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nathan Chancellor X-Patchwork-Id: 13554395 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0ADD17CD; Tue, 13 Feb 2024 02:06:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707789993; cv=none; b=XlaTpqLurxMG51Mnm6v2WtDfbrcOS/29uqq8EgpkAMcQ8ymdWi4jfjfZbdHIxPhgeouucriFbR4L0uoX8A3jAeh7pcdoncSM2QT/zBwqg8BpNEELiGisVtTP2XUqUESpN9jOB2j11+JVPyR4532HXpzAunMpTtd8wbdV/1lCKZI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707789993; c=relaxed/simple; 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b=H4sIAFXOymUC/52NQQ6CMBBFr0K6dgxTwYgr72FY0HaAidiStjYQw t2tHMHNT95P/n+bCOSZgrgXm/CUOLCzGeSpEHrs7EDAJrOQpaxKWd6g5wVo6iGuM4GKPaT3xPa zgGILLucAZA13FozSdd0hoWyuIv/NnvL4cD3bzCOH6Px6qBP+2n8sCQFBqwuirBokox8v8pams /ODaPd9/wK60mOo4wAAAA== To: masahiroy@kernel.org Cc: nicolas@fjasle.eu, ndesaulniers@google.com, morbo@google.com, justinstitt@google.com, keescook@chromium.org, maskray@google.com, linux-kbuild@vger.kernel.org, bpf@vger.kernel.org, llvm@lists.linux.dev, patches@lists.linux.dev, stable@vger.kernel.org, Nathan Chancellor X-Mailer: b4 0.13-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=3417; i=nathan@kernel.org; h=from:subject:message-id; bh=GhodOs1V2xvOg/8UtJ2cJDvK0Yy+94bNZ2qlcF51JzE=; b=kA0DAAoWHWsmkXHAGpYByyZiAGXKzqiiMLNKtKv9HTNpLWHt7NZXR3+qPImDrmxtWD1S+S6yN Ih1BAAWCgAdFiEEe+MlxzExnM0B2MqSHWsmkXHAGpYFAmXKzqgACgkQHWsmkXHAGpZowQD9HgK/ EKkJcLelCNEJj8ruFirq96NFEySH3V7/YfAazHMA/jBB7etsCJZp0turV2NVbyGj0WmJvoZnykM UoQQk2GMJ X-Developer-Key: i=nathan@kernel.org; a=openpgp; fpr=2437CB76E544CB6AB3D9DFD399739260CB6CB716 Commit 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF") changed the ELF type of .btf.vmlinux.bin.o to ET_REL via dd, which works fine for little endian platforms: 00000000 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 |.ELF............| -00000010 03 00 b7 00 01 00 00 00 00 00 00 80 00 80 ff ff |................| +00000010 01 00 b7 00 01 00 00 00 00 00 00 80 00 80 ff ff |................| However, for big endian platforms, it changes the wrong byte, resulting in an invalid ELF file type, which ld.lld rejects: 00000000 7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00 |.ELF............| -00000010 00 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................| +00000010 01 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................| Type: : 103 ld.lld: error: .btf.vmlinux.bin.o: unknown file type Fix this by updating the entire 16-bit e_type field rather than just a single byte, so that everything works correctly for all platforms and linkers. 00000000 7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00 |.ELF............| -00000010 00 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................| +00000010 00 01 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................| Type: REL (Relocatable file) While in the area, update the comment to mention that binutils 2.35+ matches LLD's behavior of rejecting an ET_EXEC input, which occurred after the comment was added. Cc: stable@vger.kernel.org Fixes: 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF") Link: https://github.com/llvm/llvm-project/pull/75643 Suggested-by: Masahiro Yamada Signed-off-by: Nathan Chancellor Reviewed-by: Fangrui Song Reviewed-by: Nicolas Schier Reviewed-by: Kees Cook Reviewed-by: Justin Stitt --- Changes in v2: - Rather than change the seek value for dd, update the entire e_type field (Masahiro). Due to this change, I did not carry forward the tags of v1. - Slightly update commit message to remove mention of ET_EXEC, which does not match the dump (Masahiro). - Update comment to mention binutils 2.35+ has the same behavior as LLD (Fangrui). - Link to v1: https://lore.kernel.org/r/20240208-fix-elf-type-btf-vmlinux-bin-o-big-endian-v1-1-cb3112491edc@kernel.org --- scripts/link-vmlinux.sh | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- base-commit: 54be6c6c5ae8e0d93a6c4641cb7528eb0b6ba478 change-id: 20240208-fix-elf-type-btf-vmlinux-bin-o-big-endian-dbc55a1e1296 Best regards, diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index a432b171be82..7862a8101747 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -135,8 +135,13 @@ gen_btf() ${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \ --strip-all ${1} ${2} 2>/dev/null # Change e_type to ET_REL so that it can be used to link final vmlinux. - # Unlike GNU ld, lld does not allow an ET_EXEC input. - printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 status=none + # GNU ld 2.35+ and lld do not allow an ET_EXEC input. + if is_enabled CONFIG_CPU_BIG_ENDIAN; then + et_rel='\0\1' + else + et_rel='\1\0' + fi + printf "${et_rel}" | dd of=${2} conv=notrunc bs=1 seek=16 status=none } # Create ${2} .S file with all symbols from the ${1} object file